From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Brezillon Subject: Re: pwm: Introduce the pwm_args concept regression Date: Tue, 17 May 2016 17:17:16 +0200 Message-ID: <20160517171716.2c69decf@bbrezillon> References: <573AAEAF.5040603@nextfour.com> <20160517103151.54d1b413@bbrezillon> <573AE8E3.2070500@nextfour.com> <20160517121632.102f7bbd@bbrezillon> <20160517120523.GC26166@ulmo.ba.sec> <573B1985.6010006@nextfour.com> <573B2025.3070408@nextfour.com> <20160517161731.0e1d7949@bbrezillon> <573B30FF.4070504@nextfour.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from down.free-electrons.com ([37.187.137.238]:35000 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755819AbcEQPRU convert rfc822-to-8bit (ORCPT ); Tue, 17 May 2016 11:17:20 -0400 In-Reply-To: <573B30FF.4070504@nextfour.com> Sender: linux-pwm-owner@vger.kernel.org List-Id: linux-pwm@vger.kernel.org To: Mika =?UTF-8?B?UGVudHRpbMOk?= , Thierry Reding , jingoohan1@gmail.com, linux-pwm@vger.kernel.org On Tue, 17 May 2016 17:55:59 +0300 Mika Penttil=C3=A4 wrote: > On 17.05.2016 17:17, Boris Brezillon wrote: > > On Tue, 17 May 2016 16:44:05 +0300 > > Mika Penttil=C3=A4 wrote: > > =20 > >> On 17.05.2016 16:15, Mika Penttil=C3=A4 wrote: =20 > >>> On 17.05.2016 15:05, Thierry Reding wrote: =20 > >>>> On Tue, May 17, 2016 at 12:16:32PM +0200, Boris Brezillon wrote:= =20 > >>>>> On Tue, 17 May 2016 12:48:19 +0300 > >>>>> Mika Penttil=C3=A4 wrote: > >>>>> =20 > >>>>>> On 05/17/2016 11:31 AM, Boris Brezillon wrote: =20 > >>>>>>> +Thierry > >>>>>>> > >>>>>>> Hi Mika, > >>>>>>> > >>>>>>> On Tue, 17 May 2016 08:39:59 +0300 > >>>>>>> Mika Penttil=C3=A4 wrote: > >>>>>>> =20 > >>>>>>>> Hi, > >>>>>>>> > >>>>>>>> commit e39c0df1be5a97e0910b09af1530bdf3de057a06, pwm: Introd= uce the pwm_args concept > >>>>>>>> causes pwm backlight to fail on our imx6 based board. I susp= ect it affects all pwm backlight setups. > >>>>>>>> With this reverted, everything works as normal. =20 > >>>>>>> Hm, just tried using a PWM backlight on an atmel board (at91s= ama5d4ek), > >>>>>>> and after applying the following patch, it worked correctly (= that's actually > >>>>>>> a bug in the PWM driver: the HLCDC PWM device is configured w= ith inversed > >>>>>>> polarity by default, and the driver was not taking that into = account). > >>>>>>> I doubt you have the same problem here since your PWM device = is not > >>>>>>> supporting polarity configuration. > >>>>>>> > >>>>>>> Could you tell me more about this bug? What are the symptoms?= Which > >>>>>>> board are you testing on (if it's not mainlined, can you shar= e your > >>>>>>> DT)? > >>>>>>> > >>>>>>> Thanks, > >>>>>>> > >>>>>>> Boris > >>>>>>> > >>>>>>> --- > >>>>>>> diff --git a/drivers/pwm/pwm-atmel-hlcdc.c b/drivers/pwm/pwm-= atmel-hlcdc.c > >>>>>>> index f994c7e..14fc011 100644 > >>>>>>> --- a/drivers/pwm/pwm-atmel-hlcdc.c > >>>>>>> +++ b/drivers/pwm/pwm-atmel-hlcdc.c > >>>>>>> @@ -272,7 +272,7 @@ static int atmel_hlcdc_pwm_probe(struct p= latform_device *pdev) > >>>>>>> chip->chip.of_pwm_n_cells =3D 3; > >>>>>>> chip->chip.can_sleep =3D 1; > >>>>>>> =20 > >>>>>>> - ret =3D pwmchip_add(&chip->chip); > >>>>>>> + ret =3D pwmchip_add_with_polarity(&chip->chip, PWM_PO= LARITY_INVERSED); > >>>>>>> if (ret) { > >>>>>>> clk_disable_unprepare(hlcdc->periph_clk); > >>>>>>> return ret; > >>>>>>> =20 > >>>>>> Symptom is entirely dark screen. > >>>>>> The board is not mainlined but the backlight part is defined l= ike :=20 > >>>>>> > >>>>>> backlight: backlight { > >>>>>> compatible =3D "pwm-backlight"; > >>>>>> pwms =3D <&pwm2 0 1000000 PWM_POLARITY_INVERTE= D>; > >>>>>> /* > >>>>>> * a poor man's way to create a 1:1 relationsh= ip between > >>>>>> * the PWM value and the actual duty cycle > >>>>>> */ > >>>>>> brightness-levels =3D < 0 1 2 3 4 5 6 7= 8 9 > >>>>>> 10 11 12 13 14 15 16 17 1= 8 19 > >>>>>> 20 21 22 23 24 25 26 27 2= 8 29 > >>>>>> 30 31 32 33 34 35 36 37 3= 8 39 > >>>>>> 40 41 42 43 44 45 46 47 4= 8 49 > >>>>>> 50 51 52 53 54 55 56 57 5= 8 59 > >>>>>> 60 61 62 63 64 65 66 67 6= 8 69 > >>>>>> 70 71 72 73 74 75 76 77 7= 8 79 > >>>>>> 80 81 82 83 84 85 86 87 8= 8 89 > >>>>>> 90 91 92 93 94 95 96 97 9= 8 99 =20 > >>>>>> 100>; =20 > >>>>>> default-brightness-level =3D <50>; > >>>>>> }; > >>>>>> > >>>>>> > >>>>>> so the polarity is in there defined. > >>>>>> The call call graphs is like : devm_pwm_get() -> pwm_get() -> = of_pwm_get() =20 > >>>>>> -> of_pwm_xlate_with_flags which used to call pwm_set_period a= nd pwm_set_polarity but now =20 > >>>>>> just update the struct values. =20 > >>>> Adding the linux-pwm mailing list on Cc for archiving. > >>>> > >>>> Do you have any local modifications? of_pwm_xlate_with_flags() i= s only > >>>> used if explicitly set up by the PWM driver and those that expli= citly do > >>>> so are: > >>>> > >>>> $ git grep -n '=3D.*of_pwm_xlate_with_flags' -- drivers/pwm/ > >>>> drivers/pwm/pwm-atmel-hlcdc.c:271: chip->chip.of_xlate =3D= of_pwm_xlate_with_flags; > >>>> drivers/pwm/pwm-atmel-tcb.c:397: tcbpwm->chip.of_xlate =3D= of_pwm_xlate_with_flags; > >>>> drivers/pwm/pwm-atmel.c:378: atmel_pwm->chip.of_xlat= e =3D of_pwm_xlate_with_flags; > >>>> drivers/pwm/pwm-bcm-kona.c:277: kp->chip.of_xlate =3D of_pwm_xl= ate_with_flags; > >>>> drivers/pwm/pwm-berlin.c:181: pwm->chip.of_xlate =3D of_pwm_x= late_with_flags; > >>>> drivers/pwm/pwm-fsl-ftm.c:445: fpc->chip.of_xlate =3D of_pwm_x= late_with_flags; > >>>> drivers/pwm/pwm-lpc18xx-sct.c:383: lpc18xx_pwm->chip.of_xl= ate =3D of_pwm_xlate_with_flags; > >>>> drivers/pwm/pwm-omap-dmtimer.c:318: omap->chip.of_xlate =3D= of_pwm_xlate_with_flags; > >>>> drivers/pwm/pwm-renesas-tpu.c:421: tpu->chip.of_xlate =3D = of_pwm_xlate_with_flags; > >>>> drivers/pwm/pwm-rockchip.c:269: pc->chip.of_xlate =3D o= f_pwm_xlate_with_flags; > >>>> drivers/pwm/pwm-samsung.c:517: chip->chip.of_xlate =3D= of_pwm_xlate_with_flags; > >>>> drivers/pwm/pwm-sun4i.c:335: pwm->chip.of_xlate =3D of_pwm_x= late_with_flags; > >>>> drivers/pwm/pwm-tiecap.c:229: pc->chip.of_xlate =3D of_pwm_xl= ate_with_flags; > >>>> drivers/pwm/pwm-tiehrpwm.c:460: pc->chip.of_xlate =3D of_pwm_xl= ate_with_flags; > >>>> drivers/pwm/pwm-vt8500.c:219: chip->chip.of_xlate =3D of_pwm_= xlate_with_flags; > >>>> > >>>> pwm-imx is not among them and since it doesn't set anything else= it > >>>> should be using of_pwm_simple_xlate(). Also, the pwm-backlight d= river > >>>> now calls pwm_apply_args() so it should still end up calling > >>>> pwm_set_polarity(). > >>>> > >>>> Can you paste the DT node that has the pwm2 label? I suspect it'= s the > >>>> one in arch/arm/boot/dts/imx6qdl.dtsi (or something similar). Th= at node > >>>> has #pwm-cells =3D <2>, so providing the polarity in a third cel= l is not > >>>> correct. The PWM core /should/ be able to deal with it correctly= , but I > >>>> think it might be worth correcting the DTS. There are a bunch of= other > >>>> DTS files that contain the same mistake. > >>>> > >>>> If that doesn't help, perhaps you can attach dmesg output to hel= p debug > >>>> this further? The PWM core is fairly silent, though, so you migh= t need > >>>> to add some debugging messages in order to be able to see anythi= ng. I'm > >>>> thinking a first step would be to make sure all of the driver ca= llbacks > >>>> get called in the sequence that they should (and with the expect= ed > >>>> parameters). > >>>> > >>>> Let me know if you need help with that. > >>>> > >>>> Thierry =20 > >>> Yes you're right the pwm-cells is <2> and polarity in dts has no = effect, and yes it > >>> uses pwm_simple_xlate of course. The polarity is ok, but somethin= g broke with this patch, > >>> looks like the pwm hw state is stuck to zero even when modified t= hru /sys/class/backlight/backlight/brightness > >>> (the values in sysfs do change). I can debug this further tomorro= w. =20 > > Are you still testing on next or did you revert a few patches (like > > this one 3a0cfa4 "backlight: pwm_bl: Use pwm_get_args() where > > appropriate")? > > Maybe that would be easier if you could share the code you're testi= ng > > with, can you push a branch somewhere? > > =20 > Hmm I am testing against linus git (4.6.0+) and it doesnt have the "b= acklight: pwm_bl: Use pwm_get_args()" yet pulled ? Maybe that explains.= =2E. > It has "pwm: Introduce the pwm_args concept" so the tree is just brok= en atm without the other parts? Yep, so that might explain. Today discovered that this commit was introducing a bug that was later fixed by other commits, so when you test the whole patchset it work. Can you try to manually apply this fix [1]? [1]http://www.spinics.net/lists/arm-kernel/msg504856.html --=20 Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com